Some useful (and fun) tutorial Git videos:

• Git For Ages 4 And Up
• RailsConf 2008 Git Talk by Scott Chacon screencast (original). 17 minutes in describes branching and (3-way!) merging.
• Lots of tutorial videos here: Gitcasts

And some regular web pages:

• The Git Parable
• Git on del.icio.us
• A git branching model (though can be applied to any VCS to be honest).
• Workflow and another branching model.

And then a touch of reality:

• Enough git!
• Git destroyed my data